US wants 'strong UK staying in a strong EU': Kerry

The United States strongly backs Britain staying in the European Union as it gears up for a referendum on its membership, US Secretary of State John Kerry told an audience in Germany on Saturday.

"Obviously, the United States has a profound interest in your success, as we do in a very strong UK staying in a strong EU," Kerry said at the Munich Security Conference.

The British government is engaged in an intensive round of high-stakes diplomacy aimed at renegotiating the terms of Britain's EU membership before holding an in-out referendum.

Prime Minister David Cameron is seeking to convince his 27 fellow EU leaders to back controversial reform proposals at a leaders' summit in Brussels on February 18-19.

"The truth is, in every decade since its founding, the EU has been tested by forces -- internal and external -- that benefited from a house divided," Kerry said.

"We know many Europeans feel overwhelmed by the latest round of challenges, including concerns about the UK's potential exit from the EU.

"I want to express the confidence of the United States... that -- as it has so many times before -- Europe is going to emerge stronger than ever, provided it stays united and builds common responses to these challenges."